Human Genetics By Diana Bivens

Autosomal Recessive Disorders Autosomes: chromosomes 1-22 many disorders are autosomal recessive Requires defective recessive allele to be passed by BOTH parents Probability of offspring having the disorder: 25% if both parents are carriers/ 0 if only one parent is a carrier.

Cystic Fibrosis (CF) 1 in 20 Caucasians are carriers Rate of occurrence: 1 in 2000 Characteristics: accumulation of mucus in lungs and digestive tract. Life expectancy depends on severity of disease and quality of treatment Many die from lung failure

Cystic Fibrosis http://player.discoveryeducation.com/index.cfm?guidAssetId=7A00691D-2F20-4F66-BE08-663F290D4E7C&blnFromSearch=1&productcode=US

Phenylketonuria (PKU) Metabolic disorder in which phenylalanine cannot be broken down Rate of occurrence: 1 in 15,000 Can result in mental retardation All infants in US are screened Reducing intake of phenylalanine until puberty can prevent retardation

PKU

Tay-Sachs Disease Metabolic disorder that affects the nervous system More common in those of Central and Eastern European Jewish descent 1 in 30 are carriers Life expectancy: ~5 years

Tay Sachs Disease http://www.pbs.org/wgbh/nova/genome/media/2809_q056_03.html

Sickle cell anemia Disorder of the Red Blood Cells Causes sickling of cells preventing normal function Lack of oxygen to organs can cause tissue damage resulting in intense pain Affects mostly those of African descent 1 in 12 African-Americans are carriers >70,000 have the disease

Sickle Cell Anemia http://player.discoveryeducation.com/index.cfm?guidAssetId=15698172-2753-4D3C-B07F-F2A6E4C09B65&blnFromSearch=1&productcode=US

Fugates of Appalachia

Autosomal Dominant Disorders Requires only ONE allele for the disorder to be passed Probability of having offspring with the disorder: 50% if one parent has the defective allele

Huntington’s Disease Results in damage to the brain Symptoms generally occur after the affected reaches 30 years old Many have children before they show symptoms Rate of Occurrence: 1 in 15,000 Life expectancy: 10-20 years after onset of symptoms Genetic screening can identify those affected before the onset of symptoms

Huntington’s Disease http://videos.howstuffworks.com/sciencentral/2921-treating-huntingtons-disease-video.htm http://www.sfn.org/index.aspx?pagename=SearchingforAnswers_FamiliesandBrainDisorders

Achondroplasia Results in dwarfism If a child inherits two copies of the dominant gene, it can be fatal. Not all types of dwarfism are caused by a dominant gene.

Sex-Linked Inheritance Alleles that are inherited on the sex chromosomes Written as superscripts on the X and Y chromosomes XªX or XªY Most sex-linked traits are associated with the female (X) chromosome

Red-Green Color Blindness Disorder in which a person cannot differentiate between red and green Allele passed on the X chromosome Disorder more common in males Males: one copy results in color blindness Females: one copy (carrier) two copies result in color blindness

Red-Green Color Blindness

Hemophilia Disorder that prevents blood from clotting properly Allele passed on the X chromosome Males more commonly affected males: one copy results in disorder Females: one copy (carrier) two copies results in disorder

Hemophilia

Multiple Alleles Many traits are controlled by more than two alleles ex. Fur color in many animals

Polygenic Inheritance when traits are controlled by two or more genes ex. Hair color, eye color, skin color, height, fingerprint patterns

Blood Types An example of several different hereditary patterns Multiple alleles: A, B, and O Codominance: A and B Recessive and Dominant:O is recessive to both A and B

Blood Types *Notice how the genotype is written for each type

Blood Transfusion Facts People with type O- blood can donate to anyone (universal donor), but can only receive type O- blood. People with type AB+ blood can receive blood from anyone (universal recipient), but can only donate to someone who is type AB+.

Mrs. Bivens’s Public Service Anouncement You CAN NOT contract HIV, Hepatitis, or any other communicable disease by donating blood You CAN save a life by donating

Environmental Influences on Heredity External factors can influence expression of genes ex. Genes code for potential height/nutrition can affect the outcome

Environmental Influences Hormone differences between the sexes can affect gene expression Ex. balding/ the allele is thought to be dominant in males and recessive in females